Range finder



July 12, 1938. F. w. GEHRKE RANGE FINDER Filed April 17, 1934 Patented July 1.2, 1938 UNITED STATES PATENT OFFICE 2,123,465 RANGE mmm.

Friedrich Wilhelm Gehrke,

Munich, Germany,

assigner to Agfa Ansco Corporation, Binghamton, N. Y., a corporation o! New York' 2 claims. (ci. 95- 40 My present invention relates to arange finder.

One o1' its objects is a process oi measuring distances. Another object isarange nder. Still another object is a range finder which can be 5 combined with a camera in a simple and eilicientl structure. Further objects will be seen from the detailed specication following hereafter'.

The method hitherto practiced for measuring o parallactic angles was to turn one of two mirror planes inclined at an angle oi' 45 to the optical axis of the camera until the obJect whenviewed directly was in register with the image oi the object reflected by the two mirrors. Another way was to compensate for the parallaxes by a controllable optical-element (lens sections, cylinder lenses or Wedges). 'I 'he invention relates to'this latter kind of distance measuring.

According to the present invention the parallactic angles are measured by displacing a negative lens or lens section mounted before the base of the range ilnder withrelation to a. positive lens placed behind the base of the range finder. Furthermore according to the invention the range finder isy connected with a Galilean view finder. To this eiiect the prism which preferably forms the base of the whole instrument is mounted so as to be movable in direction of the base together with the negative lens not forming a part of the finder in such a manner that the Galilean view ilnder can be used alone or in connection with the range nder. The parallactic angles are measured by'means of half the negative lens which isl movable perpendicularly to the direction oi vision vand constitutes either the lower or the upper portion oi.' the field of vision of the ilnder. The stationary positive lens may simultaneouslybe a part ci the Galilean view ilnder and of the range finder.v 40 -The principal advantages ofthe new range finder according to the invention consist in the' great and clear picture'which is obtained by `the arrangement of' the lens elements. Due to its compact construction the range nder .is particularly suited for use in photographic cameras. In addition, combining the range finder with a Galilean view nder provides -the possibility of utilizingthefinder alone 'or together with aV range n n'der. y o The invention will now be described with reference to the accompanying drawing in which Fig. 1 shows diagrammatically a section'view of the ilnder and the range inder on the -line i-'I of Fig. 2, the latterbeing removed 'from u the path ofthe rays of the finder;

Fig. 2 shows diagrammatically a front view oi the arrangement shown in Fig. 1, the dotted position of' the prism in- Fig. l being omitted;

Fig. 3 shows diagrammatically a front view of a modiiication oi the arrangement according 5 to F18. 2;

Fig. 4 shows diagrammatically a range finder mounted on a camera, the range iinder being shown in horizontal section on line 4-4 of Fig. 5; 10

Fig. 5 shows a front view oi' the arrangement shown in Fig. 4, and

Fig. 6 shows a perspective view of the arrangement shown in Fig. 4, the same numerals designating the same parts. 15

l is the negative lens system and 2 is the positive lens system of the Galilean nder. The negativelens 3 and the base-forming prism I, are-mounted so as to be movable with relation to the stationary positive lens 2. The prism as 20 shown in'dotted lines in Fig. 1, may be placed ,in' thev path of the rays projected through the Galilean view finder. The base oi the range finder is marked B. From Figs. 2 and 3 it is apparent that the upper part of the image viewed g5 through the finder is directly seen,A i. e. straight through the'tlnder, whereas the'lower part is seen through the prism and the negative lens 3. The negative lens 3 must be displaced until the two images are in register. Fig. 3 shows a modi- '30 flcation, wherein l' is the upper part of negative lens I. The lower part of lens l has been removed.

Figs. 4, 5 and 6 show the range nder according to this invention mounted on a camera. I g5 is the negative lens system and 2 is the positive lens system of the Galilean ilnder. The prism 4 of the range finder is embraced by a mount I which also embraces the negative lens 3 oi' the finder but admits all' the light rays necessary 40 for distance measuring. -The'refore the mount C embraces the .prism in the embodiment shown in Figs. 4 to 6 only on its lower part. The mount 6 is pressed against an abutment 9 by means oi'.-

the spring 8. The abutment 9 may be moved for. the distances smaller than infinity by any v suitable means coupled with the objective mount, for instance, as shown in Fig. 4 by one of the struts connecting the objective panel with the camera casing. 1 5 In order that with the desired long base ot' the A range ilnder the negative lens oi the Galilean iinder be arranged at a suiilciently long distance `from the eye-lena, without necessity of giving the camera,in direction oi the optical axis, the' u extension of the Galilean nder, it is advisable to place the negative objective lens of the finder in a mount which may be extended in the way of a-telescope as shown in Fig. 4. What I claim is:

1. A range finder which comprises in combination, a positive lens system, a negative lens system arranged at a substantial distance in iront of said positive lens system and limiting half of the picture eld, said positive lens systeml and negative lens system forming a Galilean nder, a prism constituting a parallelopiped arranged laterally to said nder and limited by two planes inclined to the optical axis of said I tive lens laterally in and out Aof the eld nder. i

.2. In combination with a camera, a finder which comprises in combination; a positive lens system, a negative lens system arranged at avv substantial distance infront ,of said positive lens system so that both lens systems form a Galilean view nder, means for moving said negative lens system in direction of its optical axis, a prism oonstituting'a parallelopipedV arranged laterally to said nder limited by planes inclined tothe optical axis of said finder, a negative lens arranged before the inclined plane of said prism iremote from said nder, and meansconnected.

with the objective mount of said camera for displacing said prism and said negative lens laterally towards and away from said finder.

FRIEDRICH WILHELM GEHRKE.

OI" busti 

